Figure 1

Single-cell processes in cancer. Although single cancer cells interact with their neighbors and the adjacent stromal cells, there are many biological processes that occur through the actions of individual cancer cells, shown in this illustration. These complex biological processes in human cancers include: (a) transformation from a single normal somatic cell into a tumor cell; (b) clonal evolution that occurs through a series of selective sweeps when single cells acquire driver mutations and diversify, leading to intratumor heterogeneity; (c) single cells from the primary tumor intravasate into the circulatory system and extravasate at distant organ sites to form metastatic tumors; and (d) the evolution of chemoresistance that occurs when the tumor is eradicated but survived by single tumor cells that harbor resistance mutations and expand to reconstitute the tumor mass.